Plug for deep undersea pipeline with pyrotechnic gas-generating charge - which brings about sealing off against high pressure, preventing flooding of pipeline in case of accident during laying

摘要

Device for closing off deep undersea pipelines in case of accident during laying which could cause flooding of the pipeline comprises an autonomous pressure generator, means of detecting accidents to the pipeline, mechanical means of circulation without friction in the pipeline and a seal ensuring water-tightness. The seal is constituted by a skirt in polyurethane which will be deformed and applied against the inner wall of the pipe by the expansion of a water-tight annular chamber. It possesses a central armature with supports to take up the flexibility of the skirt, and annular pockets between the central armature and the skirt. The seal is connected to a gas generator contd. in a receiver resistant to high pressure. The gases are cooled before they reach the inflatable annular pockets. A closing-off system pref. comprises two such devices connected by a cable and situated on either side of the zone where the damage can appear, e.g. the most curved part. The invention overcomes difficulties encountered with existing internal mobile pipeline closing-off devices, held by a rope from a ship to the horizontal part of the pipe, in which the closing-off mechanism is controlled by an electrohydraulic group integrated in the plug and activated by a detonator. These devices are not suitable for the pipes of small dia. used for great depths. They do not prevent the flooding of the suspended part of the pipeline connected to the laying vessel. They risk being displaced by the propagation of the crushing to the next buckle arrester and sliding in case of failure of their clamping mechanism.